TRANSISTOR PAGE INDEX
   Select a transistor topic from the list below.

Please visit our 101 Science Store
+++++++++++++++++++++++++++++++++++++++++++

The Transistor Story -

"The transistor was probably the most important invention of the 20th Century, and the story behind the invention is one of clashing egos and top secret research." 

The First Point ContactTransistor

This picture shows the workbench of John Bardeen and Walter Brattain at Bell Laboratories. They were supposed to be doing fundamental research about crystal surfaces. The experimental results hadn't been very good, though, and there's a rumor that their boss, William Shockley, came near to canceling the project.  But in 1947, working alone, they switched to using tremendously pure materials.  It dawned on them that they could build the circuit in the picture. It was a working amplifier!  John and Walter submitted a patent for the first working point contact transistor.  Shockley was furious and took their work and invented the junction transistor and submitted a patent for it 9 days later. The three shared a Nobel Prize. Bardeen and Brattain continued in research (and Bardeen later won another Nobel). Shockley quit to start a semiconductor company in Palo Alto. It folded, but its staff went on to invent the integrated circuit (the "chip") and to found Intel Corporation. By 1960, all important computers used transistors for logic, and ferrite cores for memory. Memory chips replaced core in the 1970's.

   
1. INTRODUCTION  - A transistor is a small electronic device that can cause changes in a large electrical output signal by small changes in a small input signal.  That is, a weak input signal can be amplified (made stronger) by a transistor.  For example, very weak radio signals in the air can be picked up by a wire antenna and processed by transistor amplifiers until they are strong enough to be heard by the human ear.  A transistor consists of three layers of silicon or germanium semiconductor material.  Impurities are added to each layer to create a specific electrical positive or negative charged behavior.   "P" is for a positive charged layer and "N" is for a negative charged layer.  Transistors are either NPN or PNP in the configuration of the layers.  There is no particular difference here except the polarity of voltages that need to be applied to make the transistor operate. The weak input signal is applied to the center layer called the base and usually referenced to ground which is also connected to the bottom layer called the emitter.  The larger output signal is take from the collector also referenced to ground and the emitter.  Additional resistors and capacitors are required along with at least one DC power source to complete the transistor amplifier.  You should have already studied the basic electricity and basic electronics sections of this web site and have a fairly good understanding of how resistors and capacitors effect electrical circuits.   A typical transistor amplifier is shown below.